Toluene dinitration

Nitration of MNT and DNT to TNT Old U.S S R. method (according to Gorst) Mononitration of toluene Dinitration Triniiration German method... 

Dinitration of toluene results in the formation of a number of isomeric products, and with a typical sulfuric—nitric acid nitrating mixture the following mixture ofisomers is obtained 75 wt % 2,4-dinitrotoluene [121-14-2] 19 wt % 2,6-dinitrotoluene [606-20-2], 2.5 wt % 3,4-dinitrotoluene [610-39-9], 1 wt %... 

The y -phenylenediamiaes are easily obtained by dinitrating, followed by catalyticaHy hydrogenating, an aromatic hydrocarbon. Thus, the toluenediamiaes are manufactured by nitrating toluene with a mixture of sulfuric acid, nitric acid, and 23% water at 330°C which first produces a mixture (60 40) of the ortho and para mononitrotoluenes. Further nitration produces the 80 20 mixture of 2,4- and 2,6-dinitrotoluene. Catalytic hydrogenation produces the commercial mixture of diamiaes which, when converted to diisocyanates, are widely used ia the production of polyurethanes (see Amines, aromatic, DIAMINOTOLUENES) (22). 

Toluene Diisocyanate. Toluene diisocyanate is the basic raw material for production of flexible polyurethane foams. It is produced by the reaction sequence shown below, in which toluene is dinitrated, the dinitrotoluene is hydrogenated to yield 2,4-diaminotoluene, and this diamine in turn is treated with phosgene to yield toluene 2,4-diisocyanate. 

Isocyanates. The commodity isocyanates TDI and PMDI ate most widely used in the manufacture of urethane polymers (see also Isocyanates, organic). The former is an 80 20 mixture of 2,4- and 2,6-isomers, respectively the latter a polymeric isocyanate obtained by phosgenation of aniline—formaldehyde-derived polyamines. A coproduct in the manufacture of PMDI is 4,4 -methylenebis(phenyHsocyanate) (MDI). A 65 35 mixture of 2,4- and 2,6-TDI, pure 2,4-TDI and MDI enriched in the 2,4 -isomer are also available. The manufacture of TDI involves the dinitration of toluene, catalytic hydrogenation to the diamines, and phosgenation. Separation of the undesired 2,3-isomer is necessary because its presence interferes with polymerization (13). 

If toluene is dinitrated without separation a mixture of about 80% 2,4-dinitrotoluene and 20% 2,6-dinitrotoluene is obtained. Nitration of separated 2-nitrotoluene will yield a mixture of approximately 65% of the 2,4- and 35% of... 

Dinitrotoluene, in which both nitro groups are meta to the methyl, is probably not formed during the dinitration, and 8- and e-TNT, namely 3,4,5- and 2,3,5-trinitrotoluene, are not found among the final products of the nitration of toluene. 

Typical aistribution of isomers when toluene is dinitrated is shown in Figure 2. 

Fig. 52. Nitration of toluene with HNO3-H2SO4-H2O mixture, at temperature, of di- and trinitration 65° and 80°C respectively. Area between I and II - dinitration, to the right of II - trinitration (Gorst [2]).

Normally, nitration of deactivated compounds (and therefore polynitration of toluene) is carried out using aggressive nitric acid - oleum mixtures. Dinitration of toluene with mixed acids produces a 4 1 ratio of 2,4- and 2,6-dinitrotoluenes, from which the former is isolated for manufacture of toluenediisocyanate (TDI) and toluenediamine, both of which are used in the manufacture of polyurethanes. Zirconium and hafnium derivatives catalyse nitration of o-nitrotoluene, but ratios of 2,4- 2,6-dinitrotoluene are modest (66 34).12 Dinitration of toluene using Claycop (copper nitrate on K10 clay), acetic anhydride and nitric acid in the presence of carbon tetrachloride produced dinitrotoluenes in a yield of 85% with a ratio of 2,4- 2,6-dinitrotoluene of 9 1.13 This method, however, requires a large excess of nitric acid, the use of an unacceptable solvent and long reaction times. The direct nitration of toluene to 2,4-dinitrotoluene using nitric acid over a zeolite P catalyst, with azeotropic removal of water, is reported to give a 2,4 2,6 ratio of 14, but full results are yet to be published.14... 

After our success in nitrating moderately active monosubstituted benzenes with acetic anhydride and nitric acid over zeolite p,11 we decided to try the use of trifluoroacetic anhydride and nitric acid over zeolite p for nitration of deactivated substrates. Although trifluoroacetyl nitrate is known to be more active than acetyl nitrate, it has not been widely used in nitration reactions.15 Nitrobenzene has been successfully nitrated using fuming nitric acid and trifluoroacetic anhydride in equimolar proportions at 45-55 °C.16 However, no dinitration of toluene was reported. 

In order to slow down the overall reaction we added acetic anhydride as a diluent, thereby giving the zeolite a better chance to exert an influence over the reaction. Indeed, this led to a slower reaction and zeolite HP then exerted a greater influence over both the rate and selectivity. The yield after 2 h at -10 °C in the absence of the zeolite was only 16 % and the 2 3 ratio was the usual 2 1, but with the zeolite present the yield increased to 99 % and the ratio to 17 1. p-Nitrotoluene could also be nitrated with the optimised system used for o-nitrotoluene, but the reaction was much slower. Therefore, for direct dinitration of toluene it would be necessary to minimise the amount of the diluent used. 

Dinitration of Toluene. We attempted to carry out a single step nitration of toluene (Scheme 2) under conditions similar to those developed for selective nitration of o-nitrotoluene, but using two equivalents of nitric acid and a smaller quantity of acetic anhydride. The reaction produced dinitrotoluenes in almost quantitative yield. For a 17.5 mmol reaction the selectivity was exceptional (2 3 = 25 1) using 1 g zeolite, and as high as has been reported heretofore (2 3 = 14 1) even when only 0.5 g of zeolite was used. 

Mononitration of benzene is carried out at about 60° and dinitration meta isomer) at about 95° further nitration is difficult. In a similar manner, toluene gives rise to o- and p-nitrotoluenes (90%) and a small quantity of the meta isomer, isopropylbenzene (cumene) goes predominantly to p-nitrocumene (89%), and t-butylbenzene to p-nitro-t-butyl-benzene (74%). For the nitration of an easily oxidizable substance like p-cymene, a good emulsion and careful temperature control are important. ... 

TNT, 4, is produced by the nitration of toluene with a mixture of nitric and sulfuric acids. Toluene is first mononitrated and then dinitrated, and finally crude trinitrotoluene (TNT) is produced by the trinitration step. This step requires a high concentration of mixed acids with a free SO3 group (Eq. 12.4) [4]. 

Isomer control in the mononit ration and dinitration of toluene was studied by Harris (23, 24). Both papers were dedicated to the increase ofp-niirotoluene which is an important intermediate in dyestuffs and pharmaceuticals manufacture, where both a- and m-isomers are waste products and the high proportion of 2,4-dinitrotoluene is desirable for isocyanate production. This aim was achieved by adding phosphoric acid to the nitration mixtures. 

M.iUisa ami M.iMvi [2 ) collected the technical data on dinitration of mono nitio derivjiivos of ben/ene and toluene. 

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